Projection Problem

Language acquisition can be described as solving the projection problem: determining the mapping from primary linguistic data to the acquired grammar (Baker, 1979; Peters, 1972).  When language learning is so construed, the poverty of the stimulus becomes a problem of underdetermination.  That is, the projection from data to grammar is not unique, but is instead one-to-many: one set of primary linguistic data is consistent with many potential grammars.

References:

1. Baker, C. L. (1979). Syntactic theory and the projection problem. Linguistic Inquiry, 10(4), 533-581.
2. Peters, S. (1972). The projection problem: How is a grammar to be selected? . In S. Peters (Ed.), Goals Of Linguistic Theory (pp. 171-188). Englewood Cliffs, NJ: Prentice-Hall.

(Added March 2011)